ZOOLOaY AND BOTANY, MI0RO80OPY, ETC. 133 



cation of 100 and condensing lens as above of 10 cm. opening, 1/20 of a 

 second is sufficient. 



A construction similar to that used in Marey's photographic pistol 

 may be employed to take several successive pictures of moving objects. 

 The same result may, however, be more simply attained by using 

 Janssen's principle, viz. that by quick working of the shutter sharply- 

 defined pictures can be taken on a moving plate, which need not come 

 to rest (as in Marey's apparatus) during each exposure. To this end 

 the photographic plate is pneumatically put in motion (rotation, sliding 

 or free fall) at the same time as the shutters, and the shutter A acts so 

 as to give quick successive illuminations of the object. This is effected 

 by means of a rotating slide, carrying on its periphery 10-12 sector- 

 shaped openings: one opening, viz. that behind the object before the 

 release of the slide is circular, and provided, as above described, with an 

 opalescent glass. 



Easy Method for " Photographing " Sections.* — Dr. A. Trambusti 

 says that he has obtained very excellent results from photographing 

 mounted sections in the following simple manner, which is directly 

 derived from De Giaxa's method of reproducing by coarse photography 

 cultivation- plates."]" 



A small piece of albumenized paper sensitized with silver nitrate is 

 placed on a piece of wood covered with black. To this is clipped on, 

 cover-glass downwards, the slide to be photographed, and this simple 

 apparatus is then exposed to direct or diffuse sunlight until the paper 

 outside the section has become sufficiently black. The paper is then 

 removed to a water-bath in order to remove any excess of silver nitrate 

 and after a little time placed in a bath of chloride of gold. It is next 

 fixed with hyposulphite of soda in the usual way. 



Instead of paper sensitized with silver nitrate the author has also 

 tried paper prepared with ferrocyanide. The apparatus arranged as 

 before is exposed until the olive colour is no longer perceived. It is 

 then washed in water. This completes the process. The picture ob- 

 tained by this method, which is certainly quicker than the other, is of a 

 sky-blue colour. 



A score or more of these reproductions may be made in less than an 

 hour. 



The author used preparations stained red, and expresses the opinion 

 that the results therefrom are better than with other colours. 



Chromo-copper Light-filter. $ — Prof. E. Zettnow says that the 

 copper-chromium filter is very useful for bacteriological purposes, as 

 bacilli stained red, blue, or violet come out quite black on the focusing 

 glass, and therefore a preparation (cover-glass or section) stained with 

 methylen-blue can be photographed with great brilliancy. If sunlight 

 is used and a very concentrated fluid be desired, then the following 

 mixture, diluted afterwards if required, is made : — 160 grm. copper nitrate 

 and 14 grm. chromic acid mixed with 250 ccm. of water. For general 

 purposes the following solution in a layer 1-2 ccm. thick is more con- 

 venient :~175 grm. copper sulphate and 17 grm. bichromate of potash 

 mixed with 1 litre of water. 



* Zeitschr. f. Wiss. Mikr., v. (1888) pp. 335-6 (1 pi.). 



t See this Journal, 1888, p. 827. 



i Centralbl. f. Bakteriol. u. Parasitenk., iv. (1888) pp. 51-2. 



